I was going though my pile of radios and found my Motorola SX700 FRS radios from 2005 or so. I had new replacement NiMH batteries and put them in. When putting the radios in their drop chargers, one charged nicely (lighting the red LED on the AC/DC adapter) while the other one would not cause the red LED to light unless I pushed it hard into the charger.
What the problem with my radio was that both metal springs on the battery DOOR needed to be pulled slightly out, once I did that the drop charger charged the radios as expected.
N2TIQ's radio blog 